Kinetics and mechanism of formation of adhesive joints based on ethylene-vinyl acetate copolymers

Abstract

The structure of transient zones in PVC-poly(ethylene-co-vinyl acetate), PET-poly(ethylene-co-vinyl acetate), and steel-poly(ethylene-co-vinyl acetate) adhesion systems is studied. It is shown that PET-poly(ethylene-co-vinyl acetate) and PVC-poly(ethylene-co-vinyl acetate) are related in incompatible and partially compatible systems, respectively. In the temperature range 100–180°C, diffusion coefficients and the activation energy of diffusion are determined. The depth of penetration of copolymer macromolecules into the PVC phase is calculated. The kinetics of adhesive-joint formation is studied. For all systems, the increase in joint strength has a common character; for each temperature, the steady state is attained. The results are analyzed in terms of wetting and diffusion theories. Both models satisfactorily describe the kinetics of joint formation in compatible and incompatible systems (including steel-poly(ethylene-co-vinyl acetate). The effective activation energy of the kinetics of adhesive-joint formation is determined and compared with the activation energies of diffusion, the viscous flow of copolymers, the β transition, and the rate of conformation rearrangements in the surface layers of ethylene-vinyl acetate copolymers. It is suggested that the data obtained can be generalized in terms of the Bikerman theory of a “weak boundary layer.”